The invention pertains generally to structures designed to minimize safety hazards to persons operating conventional chain saws.
It is well known that during the operation of a chain saw a hazard to the operator can arise, when the chain encounters a particularly hard object such as a knot or nail present in the wood being cut. The shock of this encounter may cause the saw to recoil upward and rearward toward the operator (hereinafter "kickback"), possibly causing serious injury to the operator.
One traditional approach to this problem has been to employ a guard, attached to the housing containing the chain saw motor, which guard normally lies in a position above and parallel to the cutting chain. Frequently this guard is pivotally attached to the housing, so that the guard will not impede the cutting operation, but instead may rotate away from the chain as the chain passes through the wood being cut and any surrounding foliage. In this arrangement a spring has been used, connecting the guard to the housing, to return the guard to its normal position after completion of each cutting operation.
One possible disadvantage of the guard is that it may in some cutting operations somewhat impede the operator's view of the cutting operation. There are some cutting operations in which it would be desirable to have an alternative safety mechanism to prevent kickback, so that the cutting operation could be performed without the guard of the type described above, to allow an unobstructed view of the cutting operation.
However, for maximum possible safety, it is desirable that the operator also have the option of using the guard in conjunction with the alternative safety mechanism. This mode of operation should be employed whenever the cutting operation is such that the guard does not present a significant view problem.
It is also desirable to have such an alternative safety mechanism which can not only prevent kickback, but can also allow the operator to adequately hold and control the chain saw with one arm, so that the operator's other hand is freed for other purposes--e.g., holding and positioning a branch or other object being cut, and controlling the fall thereof. Also such a mechanism allows the chain saw to be safely operated by a handicapped person having only one arm, or by a non-handicapped person of moderate strength.
The present invention deals with the above-described needs by providing an easily removable guard of simple design, together with a support lever projecting to the rear from the chain saw housing (the forward direction herein being the direction that the chain projects from the housing), which has a strap which bears upon the top of the forearm of the operator at the end of the support lever, so as to provide leverage against kickback; and also, in conjunction with the strap, a belt encircling the operator's forearm. This combination allows the operator to adequately hold and operate the chain saw with one arm.